Department of Pathology and Microbiology, College of Medicine, University of Nebraska Medical Center, Omaha, Nebraska, USA.
Department of Pathology and Microbiology, College of Medicine, University of Nebraska Medical Center, Omaha, Nebraska, USA
Infect Immun. 2020 Mar 23;88(4). doi: 10.1128/IAI.00943-19.
is the leading cause of bacterial sexually transmitted infections, and causes community-acquired respiratory infections. , the host immune system will release gamma interferon (IFN-γ) to combat infection. IFN-γ activates human cells to produce the tryptophan (Trp)-catabolizing enzyme indoleamine 2,3-dioxygenase (IDO). Consequently, there is a reduction in cytosolic Trp in IFN-γ-activated host cells. In evolving to obligate intracellular dependence, has significantly reduced its genome size and content, as it relies on the host cell for various nutrients. Importantly, and are Trp auxotrophs and are starved for this essential nutrient when the human host cell is exposed to IFN-γ. To survive this, chlamydiae enter an alternative developmental state referred to as persistence. Chlamydial persistence is characterized by a halt in the division cycle, aberrant morphology, and, in the case of IFN-γ-induced persistence, Trp codon-dependent changes in transcription. We hypothesize that these changes in transcription are dependent on the particular amino acid starvation state. To investigate the chlamydial response mechanisms acting when other amino acids become limiting, we tested the efficacy of prokaryote-specific tRNA synthetase inhibitors, indolmycin and AN3365, to mimic starvation of Trp and leucine, respectively. We show that these drugs block chlamydial growth and induce changes in morphology and transcription consistent with persistence. Importantly, growth inhibition was reversed when the compounds were removed from the medium. With these data, we find that indolmycin and AN3365 are valid tools that can be used to mimic the persistent state independently of IFN-γ.
是细菌性性传播感染的主要原因， 引起社区获得性呼吸道感染。在感染期间，宿主的免疫系统会释放伽马干扰素 (IFN-γ) 来对抗感染。IFN-γ 激活人体细胞产生色氨酸 (Trp)-分解酶吲哚胺 2,3-双加氧酶 (IDO)。因此，IFN-γ 激活的宿主细胞中胞质 Trp 减少。为了适应严格的细胞内生存， 已经大大减少了其基因组的大小和含量，因为它依赖宿主细胞获取各种营养物质。重要的是， 和 是 Trp 营养缺陷型，当宿主细胞暴露于 IFN-γ 时，会因这种必需营养素而饥饿。为了在这种情况下存活下来，衣原体进入一种被称为持续存在的替代发育状态。衣原体的持续存在表现为分裂周期停止、形态异常，以及在 IFN-γ 诱导的持续存在情况下，依赖 Trp 密码子的转录变化。我们假设这些转录变化依赖于特定的氨基酸饥饿状态。为了研究当其他氨基酸变得有限时，衣原体的反应机制，我们测试了原核生物特异性 tRNA 合成酶抑制剂吲哚霉素和 AN3365 的功效，分别模拟色氨酸和亮氨酸的饥饿。我们表明，这些药物阻断衣原体的生长，并诱导形态和转录发生与持续存在一致的变化。重要的是，当从培养基中去除这些化合物时，生长抑制被逆转。有了这些数据，我们发现吲哚霉素和 AN3365 是有效的工具，可以独立于 IFN-γ 模拟持续状态。
